Chapter 14 - Electrical Safety Flashcards
Electrical currents
move from high voltage to low voltage
voltage
describes the total amount of electrical force (energy) that drives the current between the two points- measured in volts
current (I)
flow of electric charge or the rate of flow of electric charge - measured in amperes (A)
Resistance
measure of the opposition to the flow of steady electrical current. Resistance (R) is measured in ohms (omega symbol)
Series Circuits
Components are connected in series along a single path, so the same current flows through all of the components.
Parallel Circuits
Electrical current to each element in the circuit is separate, so if one element was to burn out, the other resistors would still have power.
If you add an element, the other elements will still have the same amount of voltage as before. Same with removal.
Direct Current (DC)
unidirectional flow of an electric charge.
Current flows through the circuit in the same direction al all times
Alternating currents (AC)
Flow of electric charge periodically reverses direction.
Current flow passes through a regular succession of changing positive and negative values by periodically reversing its direction of flow.
Total positive and negative values of current are equal
Resistors
Elements of electrical and electronic systems that are designed to intentionally resist the flow of electrical current through the system at a known measurement
The higher the value of resistance, the lower the current will be
The primary characteristics of a resistor
the resistance, the tolerance, the maximum working voltage, and the power rating
Capacitators
passive electronic component consisting of a pair of conductors separated by a dielectric (insulator). When potential difference exists, an electric field is present, stores the energy, and produces a mechanical force between the conductors. Values measured in Farads (F).
Inductor or Reactor
Passive electrical component that can store energy in a magnetic field created by the electric current passing through. Measured in Henries. Typically a wire shaped as a coil helps to created strong magnetic field.. Used in electronics where current and voltage change with time.
Electrical Shock Hazard
Electrical current passes through the body.
Electrical Shock situations
Two wires with different voltages- body in between. Electrical components not properly grounded. Moisture (sweat, pools of water) increase risk.
Severity of injury from electrical shock depends on
Amount of current and length of time current passes throughout the body.
Ventricular fibrillation
Currents greater than 75mA
Heart Paralysis
Currents greater than 4 A
Tissue burns
Currents greater than 5 A
Burns caused by electricity
Electrical (when person touches electrical wiring or equipment- usually on hands).
Arc Blasts- powerful high amperage currents arc through the air. Arcing is luminous electrical discharge.
Electrical fires
Primary hazards associated with arc blasts
Thermal radiation and light - burns
Pressure wave blast
Droplets of molten metal form electrical equipment components
Fire extinguisher type for an electrical fire?
ABC
Electrical Accidents caused by
Unsafe Equipment / Installation
Workplace hazards
Unsafe Practices
Workplace electrical hazards
Exposed electrical parts
Overhead power lines (stay back 10 feet, warning signs, assume energized- non metal ladders, PPE)
Inadequate Wiring- wire too small a gauge for current
Defective or damaged cords and wires
To control hazards of damaged and defective cords
Insulate live wires
Inspect cords and wires before each use
Use only cords with three wire type
Use only cords, connection devices, and fitting equipped with strain relief
Remove cords by pulling on plugs not cords
Damaged or modified cords taken out of service immediately
Flexible cord safety
Do not use if inspection is difficult
Do not run through holes in walls, ceilings, or floors
Do not run through doorways, windows, etc.. unless physically protected
Do not hide in walls, ceilings, floors, or other raceways
Improper Grounding
Most common OSHA violation
If no safe path to ground for currants, exposed metal parts may become energized and hazardous
Ground Fault Circuit Interrupters
Detects difference between circuit wires- leakage current-if detected- GGCI witches off current in the circuit. Set at 5mPA- protect workers from electrocution
Assured Equipment Grounding Conductor Program
Must cover all cord sets, receptacles not part of building/structures, all equipment connected by plug and cord
Program must include- specific procedures, competent person to implement, visual inspection for damage
Overloaded Circuits
Can produce heat or arcing
Prevent with a circuit breaker or fuse
Safety related work practices
Use barriers and guards to prevent passage through areas of exposed energized equipment
Preplan work and post hazard signs
Keep working spaces and walkways clear of cords
Use special insulated tools when working on fuses with energized terminals
Do not use worn or frayed cords or cables
Do not fasten extension cords with staples, hang from nails, or suspend by wire
Training required for employees working with electrical equipment
Deenergize electric equipment before inspecting or repairing
Using cords, cables, and electrical tools in good repair
Lockout/tagout procedures and recognition
PPE
